Water, energy and material Cycles in an Afforested Watershed of Chamaecyparis Obtusa were investigated in the Ochozu Experimental Watershed in Kasuya Research Forest of Kyushu University Forest in Kyushu, Japan.(1)Results on runoffThe threshold between overland flow and subsurface runoff was estimated to be basin storage of 7.6mm that is approximately equivalent to the thickness of major hydrological activity zone. Parameters for the Storage Function Model were optimally searched by simple genetic algorithm and fuzzy linear regression. Both long-term and short-tem runoffs were estimated by TOPMODEL, a storage-type semi-distributed-parameter model. Ground water level in the riparian zone was a first-order control on the runoff phenomenon at the basin scale. The soil moisture content of the upper subsurface in the slope also related to the discharge, which implies that hydrological coupling among the slope, the riparian zone and the stream occurred the rain events.(2)Results on evapotran
… MorespirationStatistical analysis on the sampling numbers of sapwood for the appropriate application of Granier method, a sapflow measurement method, showed that at least 20 samples are required for the measurement of sapflow for Cryptomeria japonica and Chamaecyparis obtusa. The results of sapflow measurement of Chamaecyparis obtusa showed that 1) although the absolute velocities of individual sapflow varied, the their diurnal variations were almost identical, 2) transpiration rate from a single tree was increased with DBH due to increase both in sapwood area and the sap flux density. Two layers tank model well estimated the seasonal changes of runoff and evapotranspiration of the watershed.(3)Results on material cyclesWe showed that discharge is inevitable to estimate nutrient balance of watershed appropriately, and evaluated that output fluxes of both total nitrogen (T-N) and total phosphorus (T-P) exceeded the input fluxes in the Ochozu Watershed. Since most of phosphorus was transported in the form of particulate, even L-Q method, most applicable method to evaluate nutrient load, underestimated the T -P load. Less